1. Technical Field
The present invention relates generally to antenna devices. More particularly, the present invention relates to a low profile, broadband, environmentally sealed spiral shaped antenna deployable under buildings and behind building walls.
2. Related Art
Critical infrastructure and government facilities are protected from High-Altitude Electromagnetic Pulse attacks, where a destructive nuclear device such as an atomic or hydrogen bomb is detonated in the atmosphere. Specifically, the initiated nuclear chain reaction also generates electromagnetic radiation strong enough to disturb or destroy electronic circuits in the vicinity of the explosion through current overloads. Protections typically involve barrier or shield installations on the walls, ceilings, and floors of the building, such as boundary or circumferential Faraday shields. The efficacy of the shield installations, also referred to as shielding effectiveness (SE), must be evaluated periodically to ensure the facility and the critical electronic equipment residing therein is properly protected. Conventional techniques for evaluating shielding effectiveness involve the use of three separate linearly polarized antennas to cover the required frequency range, which is inefficient because of the extra time wasted by changing both antenna type and polarization multiple times in the process of test conduct. Furthermore, these conventional antennas require significant volume to use properly, which is deficient both because of the additional wasted space occupied thereby and because of their inability to be used properly in tight spaces. In particular, such conventional antennas may be as large as 4800 cubic inches. Accordingly, there is a need in the art for improved shielding effectiveness evaluation antennas. Furthermore, there is also a need for permanently deployable low profile antennas.